Duskbringer(Q): Nocturne throws a shadow blade which deals damage, leaves a Dusk Trail, and causes champions to leave a Dusk Trail. While on the trail, Nocturne ignores unit collision and has increased Movement Speed and Attack Damage.

Shroud of Darkness(W): Nocturne empowers his blades, passively gaining attack speed. Activating Shroud of Darkness allows Nocturne to fade into the shadows, creating a magical barrier which blocks a single enemy spell and doubles his passive attack speed if successful.
Unspeakable Horror(E): Nocturne plants a nightmare into his target's mind, dealing damage each second and fearing the target if they do not get out of range by the end of the duration.

Paranoia(R): Nocturne reduces the sight radius of all enemy champions and removes their ally vision in the process. He can then launch himself at a nearby enemy champion.

Runes

Jungling

For jungling I start at blue buff, proceed to wolf camp, wraiths and then mini golems. Then I port back grab long sword for extra damage and pot or two and a ward. Then I take down red buff and proceed to gank somebody. After I ward dragon and keep jungling/ganking(wherever there is an opportunity) till I get enough gold to get Madred's Razors and boots. Then just go with the flow.

Items

The items I use are pretty straight forward.- To help you jungle- Boots gain more movement speed and attack speed- For the armor penetration plus its active ability- Gain Some more defense. It has worked well so far but I'm still experimenting with other items- More critical damage- Gain extra life steal/damage.

I've also considered getting a Black Cleaver or Madred's Bloodrazors to replace the Blood Thirster and then switch up Wriggles Latern late game for more survivability like a Guardian Angel or even Randuin's Omen.

Using Nocturne's skills

When you are level six or higher you want to use your skills in this sequence:ParanoiaDuskbringerShroud of DarknessUnspeakable Horror

I like using them in this sequence because your ultimate closes the gap, duskbringer allows you to damage them, gain attack damage andkeep you on top of them constantly. By the time shroud of darkness is activated the enemy will use some ability against you to get you off of them which then by doing so allows you to attack faster plus you cancel the ability they used and then unspeakable horror will fear them allowing you all the time you need to kill them.

Also its great to use his ultimate even when you are nowhere near an enemy because if somebody is pushing a lane hard most most of the time your ult scares the **** out of them and they retreat giving a teammate breathing room or time to get back to the tower.

Conclusion

That's all I've got for now I plan on updating this guide as soon as I get more play time with Nocturne. If you have any suggestions or questions feel free to throw them out there.